This invention relates to a compressor piston wherein projections extend upwardly from an end face of the piston head from plural circumferentially spaced locations, and into a discharge port to reduce clearance volume.
Compressors are utilized to compress gases such as refrigerant. One standard type of compressor is a reciprocating compressor wherein a piston head is driven between a lower position at which a fluid to be compressed enters the compression cylinder, and an upper or xe2x80x9ctopxe2x80x9d position at which the compressed fluid is driven outwardly of the cylinder. A valve plate is typically placed at the top of the cylinder. The term xe2x80x9ctopxe2x80x9d and xe2x80x9cbottomxe2x80x9d do not refer to any vertical orientation, but instead only to a position in the cylinder. The valve plate carries both inlet and outlet valves for allowing the flow of fluid into the cylinder, and out of the cylinder at appropriate points in the reciprocating movement of the piston.
Various types of valves are known, and various types of valve plates have been utilized. One type of valve plate has a central concentric discharge valve extending around the center of the cylinder. A suction valve is placed at a location further outwardly.
The discharge valve is typically on an outer face of the valve plate, and there is a discharge port volume between the top of the cylinder and the discharge valve through the valve plate. In the prior art it is known to form a concentric ring on the compressor piston to fit upwardly into this volume and to reduce clearance volume.
One other type of compressor valving structure uses reed valves. A reed valve would typically cover a plurality of circumferentially spaced ports. In the past there has been no piston structure to eliminate the clearance space. Instead, the valve plate has been modified in various ways. However, these modifications have for the most part potentially weakened the valve plate, and thus have some drawbacks.
In the disclosed embodiment of this invention, a piston for a compressor has a plurality of circumferentially spaced protrusions extending above a nominal surface face of the piston. The protrusions fit into circumferentially isolated discharge ports in the valve plate. The discharge ports are associated with reed valves, and the protrusions ensure that the clearance volume is minimized. Minimizing the clearance volume increases the amount of fluid which is compressed during each stroke. In a preferred embodiment the piston has at least two protrusions which are non-concentric and preferably each within the same semi-circle. Further, the piston has a cutout portion extending into the nominal face of the piston for receiving the suction valve. The suction valve is preferably also a reed valve located to cover circumferentially spaced suction ports.
In this manner, the present invention provides a piston for a compressor which minimizes the clearance space in the discharge ports of valve plates utilizing reed valves, which have circumferentially spaced discharge ports. Most preferably the protrusion have frustro-conical outer peripheries to minimize or limit the restriction of gas flow during the final portion of the discharge stroke.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.